Development of method for analyzing lubricating oil additives by TLC/FTIR technique

Abstract

Additives in commercial lubricants were isolated by dialysis in rubber surgery gloves against hexane. High molecular weight additives were purified by solvent precipation with MEK and analyzed by GPC. Low-molecular weight additives were extracted from dialysate using methanol and purified by silica gel column chromatography. The identity of cach additive was characterized by IR and NMR spectroscopy. Phenolic and amine types antioxidants together with antiwear additives and viscosity index improvers were found to be presence in lubricant samples. Using isolated additives as standard, a TLC technique was developed for convenicnt identification of additives from commercial lubricants. The lubricants were analyzed by silica gel plate using carbon tetrachloride and 20% acetone in carbon tetrachloride ad eluents. Spot visualization was done by using appropriate reagents. Then each spot of additives was scrapped of the plate, concentrated and characterized by FTIR. The result was compared to those obtamed from chromatographic separation. It was found that TLC-FTIR technique could be used conveniently to characterize additives in commercial lubricants.